Firstly, the chemical equation between the calcium metal and water will be:
Ca(s) + 2 H₂O(l) → Ca(OH)₂(aq) + H₂(g)
We can see from the equation the bubbles of hydrogen gas which are formed during the reaction stick to the surface of the metal and hence calcium floats on water.
The other metal that will float on the water during the reaction is magnesium which have the same chemical behavior like calcium, we can illustrate that by the chemical equation:
Mg(s) + 2 H₂O(l) → Mg(OH)₂(aq) + H₂(g)
These atoms and other atoms in group 8A have constant valence shell.it means that all of them have 8 electrons in their valence shell (except helium that has only 2 electrons )and they don't want to attract electrons.
that s why they don't have electronegativity.
hope this helps
